<I>Attacus Atlas</I>

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Faculty Publications - Textiles, Merchandising Textiles, Merchandising and Fashion Design, and Fashion Design Department of 2013 Structure and Properties of Cocoons and Silk Fibers Produced by Attacus atlas Narendra Reddy University of Nebraska - Lincoln, [email protected] Yi Zhao University of Nebraska–Lincoln, [email protected] Yiqi Yang University of Nebraska-Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/textiles_facpub Part of the Biology and Biomimetic Materials Commons, Bioresource and Agricultural Engineering Commons, Mechanics of Materials Commons, and the Polymer and Organic Materials Commons Reddy, Narendra; Zhao, Yi; and Yang, Yiqi, "Structure and Properties of Cocoons and Silk Fibers Produced by Attacus atlas" (2013). Faculty Publications - Textiles, Merchandising and Fashion Design. 32. https://digitalcommons.unl.edu/textiles_facpub/32 This Article is brought to you for free and open access by the Textiles, Merchandising and Fashion Design, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications - Textiles, Merchandising and Fashion Design by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Published in Journal of Polymers and the Environment 21 (2013) 21:16–23; doi: 10.1007/s10924-012-0549-8 Copyright © Springer Science+Business Media New York. Used by permission. Published online November 8, 2012 Structure and Properties of Cocoons and Silk Fibers Produced by Attacus atlas Narendra Reddy,1 Yi Zhao,1 and Yiqi Yang1, 2, 3 1. Department of Textiles, Merchandising & Fashion Design, University of Nebraska–Lincoln, 234 HECO Building, East Campus, Lincoln, NE 68583-0802, USA 2. Department of Biological Systems Engineering, University of Nebraska–Lincoln, 234 HECO Building, East Campus, Lincoln, NE 68583-0802, USA 3. Nebraska Center for Materials and Nanoscience, University of Nebraska–Lincoln, 234 HECO Building, East Campus, Lincoln, NE 68583-0802, USA Corresponding author — Yiqi Yang, email [email protected] Abstract Introduction Silk fibers in the three layers of Attacus atlas (A. at- Silk fibers and protein based materials, in general, are las) cocoons have morphological structure and ten- preferred for biomedical, textile and biotechnology indus- sile properties similar to that of Bombyx mori silk. tries [1–5]. In addition to the common Bombyx mori silks, Attempts are being made to produce silk for com- silks from several other sources such as spider silks and mercial applications from cocoons of relatively un- non-domesticated silk worms such as Antheraea pernyi are known wild insects due to the unique properties of being studied for potential use in various applications [6, the fibers and as a source of income and employ- 7]. For instance, the exceptional tensile strength of spider ment. In this research, A. atlas cocoons were used to silk has been well documented and several attempts have study the chemical composition, morphology, phys- to made to produce regenerated spider silk [8]. Similarly, ical structure and tensile properties of the silk fibers it has been found that fibroin from wild silks has better in the cocoons and ability of the fibers to support potential for medical applications compared to fibroin the attachment and proliferation of mouse fibro- from B. mori silk [9]. Recent studies also suggest that, con- blast cells. It was found that A. atlas cocoons consists trary to popular belief, silk sericin also has the potential of outer, intermediate and inner layer with average for medical applications [9, 10]. Although a wide variety breaking tenacity of 4.1, 4.3, and 3.6 g/den, respec- of insects have been known to produce silk containing co- tively similar to that of B. mori silk (4.3–5.2 g/den). coons, only a few non-mulberry silks have been studied The heavier cocoons, less restrictive rearing condi- for their structure, properties and potential applications. tions and good properties of the fibers compared to Insects belonging to the saturniidae family are one of the B. mori silk makes A. atlas a potential alternative to largest group of insects known to produce cocoons con- common silks for commercial scale silk production. taining silk [11]. Among the numerous saturniidae in- A. atlas fibers had about 80 % higher optical densi- sects, Antheraea mylitta (Indian tasar), Antheraea pernyi ties of cells and extensive growth of F-actin com- (Chinese tasar), and Philosamia ricini (Eri) have been ex- pared to B. mori silk fibers. tensively studied for their structure, properties and applications [12, 13]. Silk from these wild insects is being Keywords: Wild silks, Attacus atlas, Biocompatibil- processed for commercial applications. However, the ity, Tensile properties, Bombyx mori common non-mulberry wild silk fibers are much coarser 16 P RO P ERTIES OF C O C OONS AND S ILK F IBERS P RODU C ED BY A TT A CUS A TL A S 17 than the B. mori silk [14]. Therefore, the wild silk fibers Degumming have limited applications compared to B. mori silk fibers. In addition to the three saturniidae insects A. mylitta, A. The A. atlas cocoons were separated into three layers by pernyi, and P. ricini, other insects also belonging to the sa- hand. The three layers were separately degummed us- turniidae family such as Eupackardia callata, Rothschildia ing ethylenediamene and sodium carbonate. Cocoon lebeau, Hyalophora gloveri, Actias luna, Coscinocera hercu- layers were treated in 10 % ethylenediamine and 0.5 % les, Antheraea oculea, and Copaxa multifenestrata also pro- sodium carbonate for 1 h at 80 °C with a solution to co- duce cocoons containing silk. Fibers from C. hercules were coon ratio of 20:1. Later, cocoons were washed in water found to have properties similar to that of B. mori silk and retreated in the ethylenediamine and sodium car- whereas fibers from C. multifenestrata were much coarser bonate solution at 80 °C for 15 min to complete the de- and had low breaking tenacity and breaking elongation gumming and obtain loose fibers. Degummed silk was compared to B. mori silk [15]. Likewise, Hylaphora cecro- thoroughly washed in water and dried under ambient pia cocoons were reported to consist of three layers with conditions. properties similar to that of B. mori silk [16]. However, silk produced by bag worms was found to be weak and Morphology with considerably different amino acids than those found in common silks [17]. Images of the three different layers of A. atlas cocoons In addition to obtaining fibers with unique proper- were collected using a digital camera. Surface features ties, utilizing cocoons from wild insects for commercial of the different layers in the cocoons and the longitu- silk production will provide economic benefits. Since the dinal and cross-sectional features of the degummed fi- wild insects are located in forest and tribal areas, devel- bers were observed using a variable pressure scanning oping silks from the wild insects will provide income to electron microscope (VP-SEM). Samples were sputter the indigenous people. Therefore, efforts are being made coated with gold palladium and observed in the SEM at to rear wild silks for commercial silk production [18, 19]. a voltage of 20 kV. Attacus atlas belongs to the saturniidae family which includes the common wild silks currently used for com- Composition mercial silk production. Attacus atlas insects are primar- ily found in the tropical forests and are considered to The type and percentage of amino acids in the A. at- the largest Lepidoptera insects based on their wing span las fibers was determined using a Hitachi L-8800A which exceeds 65 square inches [20]. These insects pro- amino acid analyzer. Norleucine was used as the inter- duce silk containing cocoons and the color of the co- nal standard for both the samples and the control for coons varies from silver to black depending on the host amino acid analysis. Samples were first evaporated to plant. Attacus atlas cocoons have been processed to de- dryness in a speedvac and later hydrolyzed in liquid velop yarns and fabrics. In another report, tensile prop- 6 N HCl under argon atmosphere. After 20 h of hydro- erties of the A. atlas silk fibers submerged in liquid me- lysis at 110° C, the samples were evaporated to dry- dia have also been studied [21]. It was reported that ness, then redissolved in 200 μL of 0.02 N HCl. Fifty water disrupted the protein–protein hydrogen bonds microliters was injected automatically onto the Hit- whereas ethanol enhanced the protein–protein hydro- achi Amino Acid Analyzer to determine the amino gen bonds. Significant differences in tensile properties acid type and content. In data analysis, correction was of A. atlas and spider silk were observed even though made to the amount of the internal standard, to mini- they had similar amino acid composition. The previous mize dilutional errors. research by Perez-Rigueiro was focused on understand- ing the tensile properties of the A. atlas silk fibers in liq- Physical Structure uid media [21]. In this research, we have studied the properties of the A. atlas cocoons and the silk fibers from Physical structure of the A. atlas fibers was determined the three layers in A. atlas cocoons have been character- in terms of % crystallinity and peak positions using a ized for their structure and properties in comparison to Rigaku D-max/BΘ/2Θ X-Ray diffractometer (Rigaku B. mori and common wild silks. Americas, Woodlands, TX) with Bragg–Brentano para- focusing geometry, a diffracted beam monochromator, Experimental and a copper target X-ray tube set to 40 kV and 30 mA. Fibers were powdered and compressed to form pellets Materials for the X-ray measurements. Powdered samples were used for the X-ray analysis to eliminate any preferred Attacus atlas cocoons were supplied by Reiman Gardens orientation of the crystals to the fiber axes.

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